Hi, I'm looking for some help please as this issue must have happened to somebody else. I'm building up a pair of RHS Pro Elite heads with 2.250" Ti intake valves x .311" stems. The part number is 6068. My concern is that I can't find bead locls in that size. 5/16" equates to .310" and the 8 mm LS locks equate to .3135" iirc. The 8 mm locks do lock up nicely and will probbly be fine but I'd feel happier with the correct locks if they exist. I may be splitting hairs but defo don't want a dropped valve.

Anybody come across this before? Thanks.

As long as the locks aren’t butted on the edges with each other, and there’s a little wiggle room between them, your good. If the locks touch each other at setup, find a little smaller lock, or you will risk the valve ending up in the cylinder. Personally I’ve never had an issue with 8mm LS locks on any LS head I’ve setup. A .311 stem is “almost” an 8mm stem, as I’m sure you know.

Thank you. Does this mean you've used the 8 mm locks on the .311" stems? Everything points to this being a working, safe solution but I expected 'correct' locks to be available. Argh! :-)

What 7 degree? Are you trying to use an LS retainer?

No. I’ve used the LS locks on 8mm stems. You got me wondering about this so I just went to my shop and pulled a valve out of a head I have out there. It measured .314” from tip to head. .314 isn’t quite 8mm…but the LS locks fit very nicely. I can’t tell you over the interwebs here that what your doing will absolutely work, but if you have very much experience with this stuff, you’ll know how it’s supposed to “feel” going together.
Again…as long as the locks don’t butt together, and they feel solid in the groove, I’d run it. Not sure your going to find a .311” lock.
Slide a retainer down the stem, put the locks in the groove, and pull the retainer up til it’s tight by hand, and see how it feels/looks…valve out of the head here…
This COULD mess with installed height a tad, being a couple thou smaller, so double check all of that on mock-up. Hopefully your guides were set up for this stem and the clearances are right. I hate it when folks come on tech forum and tell others to call the manufacturer…because that’s why your here…to find experienced help, but in this case as a last resort, contact RHS and ask them about these numbers, unless maybe a builder over there changed out the guides and set up the heads?

Yes, Comp Ti retainers, LS. I'll get the part number in the morning. It's late here, thanks.

Thanks Scott, yes it all feels nice and tight. Takes a decent tap to release the retainer.

you want a PAC-L8161. 5/16 for LS 7 degree hardware.

^ Thanks for that. They look interesting but I can't tell if they're bead locks. I'm looking at adverts for them now and the pics I see aren't clear enough. I'll do more checks and speak with PAC

Wowzers, on the PAC site they're described as radiused locks. Hopefully they'll locate like a bead lock. :-)

Yes, bead and radius are the same thing. The nice thing about the L8161 is it has a 5/16 radius vs an 8mm radius. The grooves are actually different sizes in each valve (5/16 vs 8mm).

No need to call PAC, you're talking to them now LOL.

Lol, I couldn't get a reply on the PAC tech extension. Obviously busy helping me on here. Thanks everybody for your help.

Mike.

LOL , sorry I am working from home today and calling back customers. I see your voicemail, and it is checked off HA.

An update. The PAC GM LS 7 degree 5/16 locks arrived today. Firstly I fitted the 8mm locks onto the .311" valve and slid up the retainer as tight as I could get it. There was some slight play, not much but it was there. When I removed the retainer the locks fell off the stem really easily.

Next I did the test with the PAC locks. There wasn't any play. Also I had to give a gentle tap to release the retainer and the locks stayed on the valve. A gentle tap dropped them out.
.
Thanks guys for your input and I'll sleep well tonight as this build is a RHS block and heads. The last thing I'd want is a dropped intake valve. .311" diameter stem. The PAC locks are .310".

Thanks to TurboBuick6 (PAC) for coming up with a solution. This question's been asked before.

Mike.

Uh, 5/16"=.3125, and 8mm is .3149. The 'nominal' may be .310" & .3135, I don't know. Either way, the locks work against the radius of each diameter, which is only a .0012" difference on the two sizes, .00175 on the nominal. It is doubtful the locks are held to tolerances any tighter than + or - .001". I say you'll be fine. Yeah, not good if you're talking valve GUIDES. But locks aren't ever going to know the .001" difference......

The groove is a different size in 5/16" and 8MM. 5/16" groove height is 0.071 and 8mm is 0.085. The radius are different as well. You start adding all these up and super close turns into not close enough.


PAC's tolerance in the ID of the locks are 0.0005" BTW.

This is an expensive build for a customer and I was feeling ou of my comfort zone with the 8mm locks. The difference in grip can be felt as I mentioned above. The retainer is rock solid/stable wih the 5/16" locks installed but has a small amount or rock with the 8mm locks.

Hey, guy, this is Mike. I drove down there last year for some Ti retainers for my PAC sprung LS7 heads. DAMN-Can't remember your name! I agree, close enough sometimes isn't good enough. BUT, any decent builder should catch the installed height diff, due to the groove height. I still think you'd be OK with the .001" diff on the radius, but installed height would be different, for sure. BTW, those Ti retainers I bought have the installed height reduced by about .040". I thought they'd be the same as the steel I was replacing? Anyway, if you remember, after 7 of my 8 Ti valves were losing the CrN coating, I replaced them with Ferrea hollow stems, which were slightly heavier, but ran tool steel retainers, not Ti. So the Ti retainers helped bring the weight back down. 31,000 miles on your dual springs (Hot Rod springs? 160lbs seat-420lbs at .600" lift? You said my springs were very popular duals for the LS), and 10,000 miles later on the Ti retainers, all is well, so a bit less of valvespring installed height is probably a good thing. Couldn't be more than a few pounds.....

I do remember you Mike. Bay area, correct?

Yup. Installed height ended up 1.750-1.760" on I, and 1.735-1.740" on E. NO valve float! BTW, I can't remember your name OR the part# on the springs. You said they're 1 of the most popular, and reasonably priced dual springs around for LS motors, if that helps. Also, I have a bit over 30,000 miles on these springs!!! VERY durable, and very satisfied with your product!!!

I remember your name now.....Hi, Matt!! Valve springs are PAC #1905. Must be a good day for the memory chip !!!! LMAO